Lithium nitride halogenides have proven themselves particularly suitable for use as solid electrolytes for light-weight batteries. Great difficulties, however, are encountered in the preparation of the extremely thin solid electrolyte layers necessary in such light-weight batteries. The use of a thin layer is necessary because the thickness of the electrolyte layer is proportional to the ionic resistance of the layer.
One method for manufacturing electrolyte layers is molding. However, in molding lithium compounds, the thin layers so obtained have limitations, depending on the substrate and the molding pressure. For example, it is not possible to obtain layers that have a thickness less than 100 .mu.m, and that are free of holes. Furthermore, the resistivity of a 100 .mu.m thick layer theoretically would be 10.sup.4 ohm/cm.sup.2, for an electrolyte resistance of 10.sup.6 ohm/cm.sup.2. In practice, however, even this value cannot be realized because a 100% degree of compression is not possible and, in addition, grain boundary resistances are observed. Unfortunately, even a resistance of 10.sup.4 ohm/cm.sup.2 is too high for many applications, especially since the total resistance of the cell comprises the resistance of the electrolyte layer in addition to the resistance of the electrodes.
The manufacture of flat layers by the molding method is also very expensive. Due to the expense and also due to the fact that there are limits with respect to the layer thickness (i.e., preparing very thin layers is fraught with difficulties), there has been an urgent need for extremely thin electrolyte layers which, on the one hand, are very light, i.e., contain lithium compounds as the solid electrolyte and which, on the other hand, have a layer thickness less than 100 .mu.m and, if possible, even less than 10 .mu.m.
It is an object of the method of the present invention to allow for the preparation of extremely thin, i.e., less than 10 .mu.m thick layers of a lithium nitride halogenide.
Significantly, these extremely thin layers are mechanically resistant and the electrolyte is in the form of a compact layer, i.e., one which is not interrupted by faults.
The method of the present invention, as recited in the claims, solves the problem of preparing an electrolyte layer that satisfies the above requirements and objectives.